“I think that he has been outspoken in saying that he wanted to curtail the Mueller investigation... This is a perilously constitutional moment, I wouldn’t say a constitutional crisis just yet… should the president go after [Deputy Attorney General Rod] Rosenstein or Mueller, it would be even worse. This is a very important moment,” Pelosi said.

“The person should not be there because of the statement’s he’s made already,” she added.

He wrote an op-ed for The Hill in May 2017 criticizing the idea of appointing a special counsel for the Department of Justice investigation.

“Serious, bipartisan congressional investigations into the Russian allegations have been under way for weeks and they have made progress. Hollow calls for independent prosecutors are just craven attempts to score cheap political points and serve the public in no measurable way,” he wrote.

Whitaker also wrote an op-ed for CNN last year in which he ripped Mueller’s reported inquiries into Trump’s personal finances and those of his family.

“It is time for Rosenstein, who is the acting attorney general for the purposes of this investigation, to order Mueller to limit the scope of his investigation to the four corners of the order appointing him special counsel. If he doesn't, then Mueller's investigation will eventually start to look like a political fishing expedition. This would not only be out of character for a respected figure like Mueller, but also could be damaging to the President of the United States and his family — and by extension, to the country,” he wrote.

Pelosi said she feared that Trump and Whitaker would try to hinder the Mueller investigation and that preserving his documents is crucial should any action be taken against him.

“Our concern is that they will interfere and say that the president is above the law…We must preserve the documents, the preservation of the documents is essential,” she said.